Electric oven heater



Feb. 7, 1928.

H. o. SWOBODA ELECTRIC OVEN HEATER Fiied Feb.l0, 192s INVENTOR JZW/MMQ Patented Feb. 7. 1928.

UNITED STATES PATENT OFFICE.

HAN S 0. SWOBODA, OF EDGEWOOD, PENNSYLVANIA, ASSIGNOR T H. O. SWOBODA, INC., OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

ELECTRIC OVEN HEATER.

Application filed February 10, 1926. Serial No. 87,307.

This invention relates to electric heating devices and more particularly to heating devices for use in domestic ovens, commercial ovens and various other chambers to be heated.

The present invent-ionrclates to a heating device especially adaptable for use in domestic cooking ovens where the device must be of a removable nature and must be of simlo ple construction and which must be so constructed that it can be easily cleaned without liability of injury.

Various forms of units for heating ovens have heretofore been devised and are in use.

In most devices of this kind, the insulators are of an extremely fragile type and are subject to easy breakage. The insulator supports are of a construction expensive to manufacture and are usually formed of sheet metal with a relatively large surface so that radiation in only one direction is possible.

The present invention has for its object to provide a heating unit wherein the insulators are of a simple construction and wherein they may be easily mounted in the frame and easily replaced when necessary.

A further object of the invention is to provide a unit which is extremely rugged, which may be easily assembled and which may be readily cleaned and wherein both sides or faces thereof are open so that heat radiation in opposite directions may be obtained.

The invention may be readily understood by reference to the accompanying drawings which illustrate a preferred embodiment 'of' the invention, but it will be understood that various changes in the construction of the device may be made within the spirit and contemplation of my invention.

40 In the drawings,

Figure 1 illustrates a plan view of a heater embodying my invention;

Figure 2 is a broken section on line II-II of Figure 1; and Figure 3 is a longitudinal section on line III-III of Figure 1.

The heating unit is comprised of two frames 2 and 2 of identically similar construction and dimensions. The two frames have registering holes at suitable points therein through which securing devices, such as bolts or screws, may be passed to secure the two members together. I have illustrated these securing devices at 3, and preferably assemble the unit with only four such thereof, are recesses 8 of substantially semicircular shape. The recesses 8 of the two members register with each other, and spool like insulators 9 having end flanges 10 are disposed in these recesses. The insulators 9 have a central opening therethrough, through which the coiled resistance wires, hereinafter described, may pass. The interior of the hole through the insulators is preferably fluted or ribbed, so that the heating wire passing therethrough has a minimum surface contact with the insulator, and space is thus provided for the circulation of air 7. through the insulators around the resistance wires.

In one end of the rim 4 of each of the frame members is a substantially rectangular opening or recess, the recess of the two members also registering, and received in the space thus provided is an elongated insulating block 12, in which there are a plurality, preferably three, of contact pins 13, 14 and 15 respectively. The central contact pin 14 a5 is preferably longer than the side contact members 13 and 15, and this longer contact member constitutes the common return pole for the resistance wire circuits.

Leading from the contact pin 13 is a resistance wire 16, which passes through the insulators 9 at the outside of the frame members until it reaches the opposite end of the frame, where it is crossed diagonally through a specially arranged insulator 17 and then continues through the inner row of insulators in the'frame to the central contact pin 14. Connected with the pin 15 is a second resistance wire 18, which is arranged similarly to the resistance wire 16, but ex- 100 tends in the reverse direction. At the crossover insulator 17, the wire 18 is wrapped about the specially arranged insulator 17, so that the wire 18 is maintained out of contact with the wire 16. The other end of the wire 1 18 also connects with the central pin 14.

The arrangement of heating wires, as thus provided, allows for the different degrees of heat which can be obtained from the heater. This is in accordance with the usual practice of providing two separate heating wires which may be connected with a source of current supply through the three-pins 13, 14 and 15, so that only one of the heating wires may be energized, or so that the two heated wlres may be connected in series, or so that the two wires may be connected in parallel with the source of current supply.

' Each of the frame members 2 and 3 may have a handle portion 19 at the forward end thereof, and pins or lugs 20 may be provided on the sides of the frame for engagement with suitable supporting racks in an oven or other chamber to be heated.

In the assembly of the device, the insulator spools are strung on the resistance wires. The resistance wires and all of the insulator elements are then laid on oneof the frame members. The other frame member is then fitted on the first, and the securing means or screws put in place to clamp the two members together. Each of the frames may be formed of cast metal, or they can be formed from pressed metal. The surface area of the metal in the device is reduced to a minimum and the construction is such that warping of the frame will be avoided.

The advantages of theinvention arise from the fact that the unit can be cheaply and easily manufactured and assembled, and when once assembled, the parts are all securely held in place. The insulators are substantially protected by the metal in the bridges and the resistance wires are prevented from overheating in the insulator by reason of the reduced surface contact obtained by the fluted holes through the insulators. v The device is extremely rugged and it can be cleaned without danger of displacing the wires or without liability of fracturing the. insulators.

While Ihave disclosed a unit which is specially adaptable for domestic ovens, it will be understood that the frame may be suitably modified and changed for adaptation to commercial ovens and other chambers to be heated.

' I claim as my invention:

1. An electric heating unit comprising a frame member having an outer rim and cross bridges thereon, said bridges having recesses therein, the rim also having a recess therein, a connector carryin insulator in the recess of the rim, spoollike insulators in the recesses of the cross bridges, a second frame member fitting over the first and co operating therewith to retain the insulators in place, said second frame being substantially identical with the first, and interchangeable therewith, and a heating wire passing through the several spool-like insu lators, said wire and insulators being removable as a unit"upon separation of-the .frame members.

2. An. electric. heating unit including a supporting frame having a plurality of spaced apart insulators retained therein and arranged in rows around the frame, a heating wire carried by substantially half of the insulators in the outer row and then crossing to the insulators of the inner row, and a second heating wire reversely arranged with respect to the first.

3. An electric heating unit including a supporting frame having a plurality of spaced apart insulators retained therein and arranged in rows around the frame, a heating wire carried by substantially half of the insulators in the outer row and then crossing to the insulators of the inner row, and a second heating wire reversely arranged with respect to the first, the wires at the crossing point being separated by a single insulator through which one of the wires passes and over which the other wire passes.

4. A heating unit comprising a pair of cooperating frame members having a plurality of spool-like insulators confined therebetween, and a heater wire passing through. the insulators, said insulators having ribbed central openings therein through which the wire passes, the ribs in the openings serving to reduce the surface contact between the wire and the insulators.

5.- In a heating unit, a pair of opposite frame members each comprising peripherally disposed rims, the'frame members being adapted to be placed face to face and each having similarly recessed bridge elements extending between the respective rims, insulators in the recesses between the members, a heater wire threaded through the insulators, means for detachably securing the frame members together in face to face relation, whereby the insulators and the heater wire may be removed upon separation of the frame members.

6. An electric heating unit including a supporting frame, insulators carried by the frame, two heating wires extending in opposite directions peripherally of the frame, a connecting terminal common to both of the wires and located at one edge of the frame, a single terminal at each side of the said common terminal for the opposite ends of the two wires, the said last-mentioned terminals being equally spaced from the common terminal, each wire extending substantially around the frame so that either will produce a practically uniform temperature over the surface of the supporting frame.

7. An electric heating unit wherein different heats are secured by a system of multiple-series control, including a frame having outer and inner rims and having two heating wires, one common terminal for the two wires, two individual terminals, one for each of the other ends of the two wires, the common terminal being positioned on one side distance along the outer rim of the frame and a part of the distance along the inner rim of the frame, whereby said wires may .1 be of substantially equal length, andwhereby the frame may be placed with either side'up in an oven while maintaining the proper position of the terminals for a multiple-series control connector.

8. A reyersible electric heating unit for multiple-series control, including a supporting frame, insulators carried by the frame, two peripherally extending heating elements in the insulators in the frame of substantially equal resistance and gauge, the areas of the frame traversed by the two elements being substantially coextensive, a common terminal to which one end ofeach of the elements is connected, and two se arate termi- 'nals for the other ends of eac of the elements, the separate terminals being symmetrically disposed with respect to the common terminal, whereby the position of the frame may be reversed without changing the multiple-series connections, and whereby substantially uniform distribution of heat is secured.

9. In a heating unit, a pair of opposed frame members each having a plura ity of similarly recessed bridge elements ermanently secured thereto, insulators received in the recesses between said members, a heater element carried by said insulators and extending substantially peripherally of the frame members,and independent fastening means passing directly through the frame members for clamping the insulators between said bridge e ements.

10. In a heating unit, a pair of opposed frame members, a plurality of bridge ele ments secured to each frame member, at

least some of the bridge elements extending in angular relationship to other of the bridge elements, insulators adapted to be clamped between the bridge elements of the frame members, and means for holding a pair of frame members in assembled relationship.

11. In a heating unit, a pair of opposed frame members, a plurality of bridge eles ments secured to each frame member at least some of the bridge elements extending in angular relationship to other of the bridge elements, insulators adapted to be clamped between the bridge elements of the frame members, and means for holding a pair offrame members in assembled relationship, said frame members being interchangeable one with respect to the other.

12.In a heating unit, a pair of frame members each comprising inner and outer rims, bridge elements between said rims, insulators adapted to be secured in position between the bridge elements of adjacent members, and means for holding a pair of framemembers in position.

13. In a heating unit, a pair of frame members each comprising a plurality ofperipherally extending rims, bridge members.

connecting said rims,'insulators cooperating with said bridge members, and means for holding a pair of frame members in cooperative relationship.

14. In a heating unit, a supporting frame, and a plurality of substantially peripherally extending heating elements carried by said frame, said elements crossing each other at one point in the frame.

15.- In a heatin unit, a plurality of separable frame mem rs, insulators carried by said members to accommodate peripherally extending heating elements, and heatin elements extending peripherally of said rame members.

In testimony whereof I have hereunto set my hand.

HAN S O. SWOBODA. 

